Abstract: A method of depositing a dual layer top clad for an optical waveguide of a planar lightwave circuit (PLC). The method includes a first step of providing a high flow rate of a Boron dopant gas for a first top cladding layer deposition process. Then, a low flow rate of a Boron dopant gas is provided for a second top cladding layer deposition process. The second top cladding layer deposition process is performed directly on the first top cladding layer deposition. The first and second top cladding layer deposition processes are combined to form a dual layer top clad of the PLC having a high Boron portion covering a plurality of optical cores and a low Boron portion covering the first portion. The first top cladding layer deposition process can comprises three deposition and anneal cycles using the high flow rate for the Boron dopant gas. The three deposition and anneal cycles are used to fill gaps between the plurality of optical cores of the PLC.

Abstract: A method of depositing a top clad layer for an optical waveguide of a planar lightwave circuit. A GeBPSG top clad layer for an optical waveguide structure of a planar lightwave circuit is fabricated such that the top clad layer comprises doped silica glass, wherein the dopant includes Ge (Germanium), P (Phosphorus), and B (Boron). In depositing a top clad layer for the optical waveguide, three separate doping gasses (e.g., GeH4, PH3, and B2H6) are added during the PECVD (plasma enhanced chemical vapor deposition) process to make Ge, P and B doped silica glass (GeBPSG). The ratio of the Ge, P, and B dopants is configured to reduce the formation of crystallization areas within the top clad layer and maintain a constant refractive index within the top clad layer across an anneal temperature range. A thermal anneal process for the top clad layer can be a temperature within a range of 950C to 1050C.

Abstract: A method and apparatus for controlling waveguide birefringence by selection of a waveguide core width for a tuned top clad is described herein. A tuned top cladding describes a pre-existing dopant concentration within a top cladding material. Given a tuned top cladding composition, a width of the waveguide core is pre-selected such that birefringence is minimized, i.e., a zero, or near zero. The desirable width of the waveguide core is determined by calculating the distribution of stress in the top cladding over a change in temperature. From this distribution of stress, a relationship between the polarization dependent wavelength and variable widths of the waveguide in the arrayed waveguide grating are determined. This relationship determines a zero value, or near zero value, of polarization dependent wavelength for a given range of waveguide widths. Accordingly, the width of the waveguide may be selected such that the polarization dependent wavelength is minimized.

Abstract: In a planar lightwave circuit, a method of making an optical waveguide that resists core deformation. The method includes a step of forming a core layer on a bottom clad. A waveguide core is formed from the core layer using an etching process. The waveguide core is fabricated to have a higher refractive index than the bottom clad. A silica glass cap layer is then formed over the waveguide core and the bottom clad. A top clad is then formed over the waveguide core, the silica glass cap layer, and the bottom clad. The waveguide core has a higher refractive index than the top clad. The silica glass cap layer maintains the shape of the waveguide core during an anneal process of the top clad. The silica glass cap layer can be deposited using PECVD (plasma enhanced chemical vapor deposition). The silica glass cap layer can be between 0.3 to 2 microns thick. The silica glass cap layer can be undoped silica glass.

Abstract: A method of depositing a core layer for an optical waveguide structure of a planar lightwave circuit. A GePSG core for an optical waveguide structure of a planar lightwave circuit is fabricated such that the optical core comprises doped silica glass, wherein the dopant includes Ge and P. In depositing a core layer from which the optical core is formed, two separate doping gasses (e.g., GeH4 and PH3) are added during the PECVD process to make Ge and P doped silica glass (GePSG). The ratio of the Ge dopant and the P dopant is configured to maintain a constant refractive index within the core layer across an anneal temperature range and to reduce a formation of bubbles within the core layer. The ratio of the Ge dopant and the P dopant is also configured to reduce refractive index birefringence within the core layer across an anneal temperature range. A thermal anneal process for the core layer can be a temperature within a range of 900 C. to 1200 C.

Abstract: A method of making a polarization insensitive optical waveguide structure. An optical core layer is formed on a substrate, wherein the optical core layer has a higher refractive index than the substrate. A mask is formed over the optical core layer. The unmasked areas of the optical core layer are then over-etched to define the core, wherein the over-etching removes the unmasked area of the optical core layer and a portion of the substrate disposed beneath the unmasked area, and defines the optical core. The mask is subsequently removed from the optical core. A cladding layer is then formed over the optical core and the substrate, the cladding layer having a lower refractive index than the optical core, to form a polarization insensitive optical waveguide structure. The amount of over-etching can be controlled to control an amount of substrate disposed beneath the unmasked area of the optical core layer that is removed.

Abstract: A method for performing high aspect ratio gap fill during planar lightwave circuit top clad deposition. A plurality of waveguide cores are formed on a substrate, the waveguide cores having a plurality of gaps there between. A cladding layer is formed over the waveguide cores and the substrate using a high-density plasma deposition process. The refractive index of the waveguide cores are controlled by using a dopant to be higher than the refractive of the cladding layer. An anneal process is performed on the cladding layer after the high-density plasma deposition process. The gaps between the waveguide cores can be smaller than 2 microns. The aspect ratio of the gaps between the waveguide cores can be greater than 3. The high-density plasma deposition process provides a very high purity USG (undoped silica glass) and BPSG (Boron Phosphorous silica glass) layers having a uniform refractive index.

Abstract: This relates to optical devices such as planar light-wave components/circuits which are designed to have a high waveguide pattern density effecting a higher etch selectivity and overall improved dimensional control of the functional waveguides on the optical device.